Adaptations in Xenylla maritima and Anurophorus laricis (Collembola) to Lichen Habitats on Alpine Rocks

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Abstract
Adaptations to climatic extremes were studied in 2 collembolan species, X. maritima and A. laricis, inhabiting lichens on alpine rocks 1200-1250 m above sea level at Finse, South Norway. Both species show seasonal variation in cold hardiness. Gut evacuation and accumulation of cryoprotective substances during autumn result in an ability to supercool to temperatures below normal winter temperatures. An exceptionally cold period in Jan. 1979, however, killed most animals on unprotected sites of the rocks. The great ability of the 2 spp. to tolerate anaerobic conditions is important to survive periods in winter when the rock surface is enclosed by an ice crust. Adaptation to dry conditions was evident from the great ability of both species to survive drought stress. They also reproduce later in the season than most other collembolan species, thus reducing the risk for the sensitive hatchlings to emerge during the driest periods of summer. In all these aspects X. maritima and A. laricis differ greatly from Collembola of climatically protected habitats. Tetracanthella wahlgreni inhabiting the surrounding lichen heath is also highly adapted to cold and anaerobic conditions, but is more susceptible to desiccation than the 2 rock species. The comparison with T. wahlgreni emphasizes humidity as an important factor structuring the spatial distribution of collembolan species.